Osteoarthritis (OA) is a debilitating and degenerative joint disease that affects more than 25% of the adult population in the United States. Altered mechanical loads, such as those due to obesity or joint injury, are implicated as initiating factors for OA. Some forms of loading, however, such as physical therapy and exercise, are used to treat OA. The mechanisms by which mechanical loading shifts the homeostasis of cartilage metabolism from anabolic to catabolic is not known. The goal of the proposed study is to elucidate the mechanisms by which biomechanical signals regulate articular cartilage homoeostasis via changes in the cellular anti-oxidant defense system and the net oxidative state. I hypothesize that the duration and magnitude of cyclic mechanical loading are critical mediators of the balance between pro- and anti-oxidant responses that determine the net oxidative and energetic state of the cell. I will test this hypothesis using a bovine articular cartilage explant model with an in vitro dynamic tissue compression system. I will determine the effect of a range of physiologic to hyper-physiologic cyclic mechanical loads on cartilage matrix homeostasis and the net oxidative, energetic, and inflammatory state of chondrocytes. Having identified a set of loading conditions that elicit an adaptable (i.e., homeostatic) versus a maladaptive (i.e., oxidative modification) response, I will then determine the effect of these loading conditions on pro- and anti-oxidant transcriptional and proteomic responses and the total cellular anti-oxidant function. Finally, to better understand the signaling pathways involved in the anti-oxidant response, I will use targeted anti-oxidant pre-treatments to identify the role of specific pro-oxidants in altering biomechanically-induced pro- and anti-oxidant functions. The proposed research will examine how biomechanical pre-conditioning of cartilage to pro-oxidants may produce compensatory anti-oxidant responses to maintain oxidative homeostasis. It will also delineate how the use of anti-oxidants, for the prevention or treatment of OA, may interfere with signaling pathways involved in normal adaptive responses to biomechanical loading. This award will support my training in the biomechanical basis of cellular metabolic and oxidative homeostasis. The mentor's lab and the Free Radical Biology and Aging program at OMRF is the ideal setting for receiving training in this area. I will receive support from a critical mass of investigators with expertise in musculoskeletal biomechanics, oxidative response pathways, and proteomic and genetic analysis. In future studies, I plan to use the expertise and techniques acquired through this award to apply new concepts to functional tissue engineering of musculoskeletal constructs that could improve cell survival and tissue function following implantation into pro-inflammatory and pro-oxidative sites of injury. PUBLIC HEALTH RELEVANCE: This project will investigate the role of biomechanically-induced oxidative and anti-oxidative processes in the normal homeostasis of articular cartilage. It may provide new insights into the prevention or treatment of osteoarthritis by identifying the role of mechanical factors in stimulating endogenous anti-oxidant processed in cartilage tissue.